This invention relates to a method for obtaining dimensionally and structurally stable objects, in particular disposable containers, starting from flexible film, and an object obtained by the method.
Disposable containers are known obtained from sheets of resistant paper, generally plastic-coated, which are unwound from reels and subjected to successive welding, folding and possibly forming processes to assume the desired spatial shape. Their filling with liquid, granular or powdery products can be effected either during the container formation or after it has been completely formed.
These known disposable containers are advantageous in terms of their stability, stackability, shelf display, strength, product protection, ease of preservation, use and reclosability. However they are rather heavy and costly, and are difficultly disposable as they are difficult to crumple.
Flexible disposable containers obtained from plastic film such as polyethylene are also known, these being essentially free of the drawbacks of rigid containers. In particular, they are of low cost, small overall size, of easy disposal, and simple, practical and advantageous to machine-fabricate starting from reels. They are however virtually without dimensional stability and consequently not easy to stack, while in addition having commercial limitations as they cannot be displayed on shelves.
U.S. Pat. No. 3,648,834 discloses a method of forming a package from a flexible film containing a plasticizer or other constituent which is capable of being polymerized upon being irradiated from a high energy source. After enclosing a product in such a packaging film, the thus formed package is subjected to a controlled amount of irradiation from a high energy source to produce cross-linking within the plasticizer or other constituent which results in the flexible packaging film becoming rigid.
An object of the invention is to eliminate the drawbacks of known containers of the various types while at the same time retaining their advantages.
U.S. Pat. No. 3,648,834 discloses a method of forming a package from a flexible film containing a plasticizer or other constituent which is capable of being polymerized upon being irradiated from a high energy source. After enclosing a product in such a packaging film, the thus formed package is subjected to a controlled amount of irradiation from a high energy source to produce cross-linking within the plasticizer or other constituent which results in the flexible packaging film becoming rigid.
An object of the invention is to eliminate the drawbacks of known containers of the various types while at the same time retaining their advantages.
A particular object of the invention is to obtain disposable containers, and objects generally, which present dimensional stability while at the same time being of low weight and cost and able to be crumpled to reduce their volume after use for easy disposal.
A further object of the invention is to provide disposable containers, and objects generally, starting from flexible film which before forming the container can be wound in a roll and hence occupy a considerably reduced space, to be stiffened only at the moment of formation of the container.
These objects and others which will be apparent from the ensuing description are attained by a method for obtaining dimensionally and structurally stable objects, in particular disposable containers, from flexible film, rewindable on a reel, by:
preparing a flexible film rewindable on a reel, which, at least in those regions which in said obtained object are required to be substantially rigid, is associated with a structurally transformable substance inert with respect to said film and at least one passive activator therefor,
forming an object from said film forming material prepared in this manner, and
during any one stage in a formation of said object, administering an energy compatible with said activator to start a structural transformation reaction of said substance and convert said regions from flexible to substantially rigid.